The present invention relates generally to compositions and methods for deacidification treatment and preservation of printed cellulosic materials, such as books, manuscripts and other image and information bearing documents and publications and works of art on paper, which may deteriorate or which may have become deteriorated through aging.
During the past 150 years, archives and libraries have struggled to prevent the aging of paper, i.e., yellowing and embrittlement of paper in documents and books. Many treatments to avoid or stop this aging have been proposed. The primary goals of these treatments are to either transform the paper into another, more stable medium or stabilize the paper against aging by deacidification. Deacidification has advantages in its effectiveness for many more years, availability of stabilized materials for use, and lower unit treatment costs.
Although previously known treatments reduce the rate that books and documents are aging, all known methods have the potential to deface or otherwise so harm significant portions of the collection so that the items are rendered unsatisfactory for ordinary use. Furthermore, numerous problems and environmental concerns exist with current treatment methods.
Moisture variation in anhydrous raw materials presents a significant problem when using most known treatment methods. As the quantity of moisture increases, either powder or gel precipitates will be formed, depending on time, reactivity, temperature and pressure conditions. These precipitates may prevent (poison), impede (slow) a manufacture or reaction rate and detrimentally affect the deacidification workability of solutions (clog paper substrates). The precipitates also may deposit on and deface books and documents and block or clog filters, pipes, valves and other restricted passages in processing equipment. They may also deposit thick coatings on walls of tanks and, depending on relative densities, separate into top or bottom phase composition layers or even, in extreme cases. actually turn the treating solution (initially thinner than water) into an immobile gelatin-like gel.
Although produced, ultra-low moisture alcohol and aliphatic hydrocarbon solvents are not available commercially in standard containers, e.g., in 5-gallon pails or 55-gallon drums. Industrial solvent manufacturers do not deliver their solvents in an ultra-dry condition, i.e., below 15 or 25 ppm. For example, the maximum moisture content specification for a 55-gallon drum of research grade xe2x80x9canhydrousxe2x80x9d methanol from Fisher Scientific is 1,000 ppm.
Sub-micron (less than 0.2 microns) coal black particles are known to precipitate in concentrates prepared for current treatment methods. The particles may be introduced as trace heavy metal (iron, cobalt, copper, etc.) impurities in the metals reacted with alcohols to produce alkoxide powders for use in treatment or by external conditions. These particles contaminate and discolor the treatment concentrate and must be removed before use in preservation. Additionally, allowing the particles to agglomerate naturally then filtering through a 0.2 micron absolute membrane filter limits the concentration of treatment concentrates that can be manufactured. For example, concentrations of organic magnesium of up to only 25 percent by weight in methanol are a maximum.
The more alkaline pH values produced by organic magnesium carbonate treatments may cause undesirable color changes. These treatments may cause sensitive inks, pigments, and dyes to change color when the cellulosic material is changed from a deteriorating acidic condition to a stable alkaline condition.
The traditional CFC and HCFC solvent systems for organic metal carbonate deacidification compositions tend to deface or damage some types of inks and or cause structural book components to dissolve or soften. The more sensitive inks soften, bleed, strike through, offset, and in some cases, even glue the leaves of pamphlets and books together into solid blocks. In addition, the use of chlorofluorocarbon solvents is generally prohibited by environmental regulations.
Despite extensive efforts and the many solutions proposed for stopping aging, a truly satisfactory method that extends the useful life of cellulosic materials for hundreds of years has not been developed. No effective treatment is known that is acceptable for essentially all paper, inks, pigments, media, or other components of printed materials and is not hazardous to users.
Accordingly, it is a principal object of this invention to provide improved deacidification compositions and methods for making them, for preserving printed and written cellulosic materials, such as books, drawings, maps, works of art, manuscripts and images.
It is an additional object of this invention to provide a method for universally preserving these cellulosic materials bearing printing, writing, drawings, or other recordings, with little or no impairment of inks, images, bindings or other visual or structural features.
These and other objects of the invention will become apparent from the following specification and accompanying drawings.
Generally, in accordance with the present invention, a deacidification composition for treating printed cellulosic materials is provided. A method of making the composition and a method of preparing components of the composition also are provided. In an important aspect, the composition comprises a metal carbonate, an ultra-dry alcohol having a moisture content of less than about 100 ppm and an ultra-dry solvent having a moisture content of less than about 100 ppm, the solvent selected from the group consisting of alcohols, aliphatic hydrocarbons, fluorocarbons and blends thereof, in amounts effective for treating and preserving printed cellulosic materials.
The deacidification treatment compositions of the present invention are made by first treating alcohol, fluorocarbon, aromatic hydrocarbon or aliphatic hydrocarbon solvents with a molecular sieve or other desiccant to reduce the moisture content below 100 ppm, to produce ultralow moisture solvents. An organic metal alkoxide is blended with the ultralow moisture alcohol solvent and carbon dioxide to form an organic metal carbonate composition. Submicron-sized magnetic impurities from the organic metal carbonate composition are removed using magnetic filtration. Then the organic metal carbonate composition is filtered through a submicron filter to produce a deacidification treatment concentrate. Finally, the deacidification treatment concentrate is blended with the ultralow moisture solvent to provide a deacidification treatment solution having relatively inert solvation characteristics toward inks and structural components of printed cellulosic materials. This composition can be used in any known method of treating printed cellulosic materials.
The ultra-dry solvents, which generally are available in standard volume commercial containers, are made in a process comprising passing the solvent through one or more drying columns. The solvent then is recirculated to the container, with re-circulation of the solvent through the container and column occurring for a period effective for reducing the moisture content to less than about 100 ppm to provide an ultra-dry solvent.
For purposes of the invention, xe2x80x9cmetalxe2x80x9d or xe2x80x9cmetal agentxe2x80x9d means organic aluminum, magnesium, zinc or blends thereof. As used herein, xe2x80x9cmetal alkoxidexe2x80x9d means an organic aluminum alkoxide, magnesium alkoxide, zinc alkoxide or blends thereof. As used herein, xe2x80x9cmetal carbonatexe2x80x9d means an organic aluminum carbonate, magnesium carbonate, zinc carbonate or blends thereof.